1. Field
Embodiments of the present invention relate to in-situ metrology in a vacuum processing chambers and more particularly to in-situ optical critical dimension (OCD) metrology (e.g., scatterometry) of a workpiece processed in the vacuum processing chamber.
2. Discussion of Related Art
Vacuum processing systems are ubiquitous in semiconductor fabrication. Certain vacuum processing chambers are configured to process a workpiece with a plasma or glow discharge. For example, a plasma etch process may pattern a feature in the workpiece based on a photo lithographically defined pattern. To reduce the feature sizes for a given photo lithographic technology node, a self-aligned double patterning (SADP) method may be employed where controlling a plasma etch process to a critical dimension and/or pitch is determinative. For example, a typical SADP processing includes trimming a mask from a first 1:1 line:space pitch to a 1:3 line:space pitch and then generating, from the trimmed mask, a double patterned spacer mask having reduced critical dimensions and a final line:space pitch of 1:1. As such, SADP processing is highly dependent on plasma etch CD, profile, and/or pitch control.
While critical dimensions of features may be deduced via OCD techniques, the difficulty in positioning an optical probe spot over a diffraction grating test structure with sufficient accuracy has hindered application of true in-situ metrology that can determine pre-etch, during-etch, or post-etch CD. Therefore, to date, OCD metrology has been limited to the integration of a stand-alone metrology station with a plasma processing platform with a workpiece either measured in the metrology module, or processed in the processing chamber, but not processed and measured (concurrently, or otherwise) within a same platform module. As such, compared to a current integrated metrology tool, true in-situ metrology would, for example, improve the throughput of a processing platform because a “pre” and “post” measurement external to the processing chamber becomes unnecessary.